Dan DiMicco said the UK would get priority status because it was America’s “friend” and was quitting the EU for good reasons.
Mr Trump, whose campaign has been engulfed by controversy after a 2005 video emerged of him making obscene comments about groping women, shares the stance of his rival Hillary Clinton that the proposed US-EU trade deal needs scrapping.
Asked if Mr Trump would put a British trade deal ahead of an EU one, Mr DiMicco told the BBC “Absolutely.
“First off, they are our friends, they have always supported us, and we’ve worked together, and they are leaving the EU in our estimation for the right reasons.
“They have lost control of their economy, the job creation engine, so why shouldn’t we be working with like-minded people before we do a deal with anybody else?”
The comments are in marked contrast to President Obama who provoked fierce controversy during the EU referendum campaign when he warned the UK would be “at the back of the queue” for a deal if it chose Brexit.